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tahoe07 -> RE: A Q's about my 08 LTZ (5/8/2008 5:44:52 PM)
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The problem is the programming. This is an excerpt from an Edmund's report explaining why the dyno numbers seemed off on the 6.0 they tested
Might be the same for the 5.3
As it turns out, the explanation boils down to an engine calibration strategy. GM calibrated the 367-hp 6.0-liter V8 to remain in stoichiometric "closed-loop" fuel delivery mode for 4 seconds after the throttle is floored. This fueling strategy helps keep emissions in check (and saves fuel) at the expense of reduced power — about 40 hp less at the peak. Once the driver lifts his right foot from the wide-open throttle position, the 4-second clock resets.
This explains why the Silverado's power is low everywhere on the graph right up to the jump in power right before redline. Corresponding to the expiration of the 4-second window, the jump in power is indicative of the engine switching to open-loop "power enrichment" mode. It is only when operating in this mode that the engine delivers its full rated power.
Release the hounds
On the road, the Silverado's full advertised power will be on tap during extended full-throttle conditions such as towing, or any other situation in which the throttle is floored for more than 4 seconds.
Be aware, however, that the Silverado's horsepower herd will be thinned out during all but the most prolonged wide-open throttle squirts around town. And with an empty bed and no trailer, 4 seconds is a fairly long time to have the throttle matted.
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